Producing toluene



Patented AugaZl,

Alexl G. oblaa, einen, 1u., signor to standard gli Company, Chicago,Ill., a corporation of diana Application December 12, 1.940, Serial No.l369,843

` (ci. 26o-ses) 7 Claims.

'I'his invention relates to a process of producing toluene frompetroleum hydrocarbons. An object f the invention is to produce bothtoluene and high knock rating motor fuelsimultaneous` ly-with the aid ofcatalysts without the destruction of large amounts-of' thepetroleumhydrocarbons such as occurs in the case of high tem- Referringto the drawing, heavy naphtha is chargedby line I0 to heater Il whereinit is vaporized and heated to a high conversion tem- I perature andconducted by transfer line I2 to reaction chamber I3 where it fundergoesconver- Vsion in the presence of a catalyst. `The naphtha peraturepyrolysis for the production of toluene from petroleum. Other and moredetailed objects will be shown in the description of the invention.

In the manufacture of benzene and toluene from petroleum by hightemperature pyrolysis. for example, at temperatures of the order of 1400F. to 1600 F., a large proportion of the paran hydrocarbons is degradedto coke ,and permanent gases. Yields of aromatic distillates andparticularly toluene are relatively low. .I have now discovered thatbythe use of catalysts at moderate temperatures within the crackingrange, I may obtain substantial yields of toluene from petroleum naphthaaccompanied by relaemployed in my process may suitably be either`straight run or cracked petroleum naphtha, preferably the former.

I prefer to employ a heavy naphtha having an initial boiling point ofabout 200 to 300 F. and-a iinal boiling point of about 450 F.- Somewhatheavier naphthas may be employed, however, including a material commonlyclassed as kerosene and a light gas oil having iinal boiling -points ashigh as 600 to 650 F. Parailinic and olenic naphthas may be employedthough somewhatA better yields of toluene are obtained from the morearomatic or naphthenic types of naphtha.

' able catalyst for eiecting conversion or reformnve1y 4lime degradationofthe naphtha into gas and carbon.

\ 4 Myprocessinvolves treating petroleum naph-` tha in two successivesteps under specific conditions of catalyst treatment and separation ofintermediate products.- In the rst step of vmy process the petroleumnaphtha is treated under aromatizing conditions in the presence ofahydrogenation-dehydrogenation catalyst at elevated temperature wherebythe aromatic hydrocarbon content of the naphtha is greatly increased,partly by cyclization of parailinic and/or l oleilnic hydrocarbons andpartly las a result of dehydrogenation of naphthenic hydrocarbons.Toluene is separated from the products and higher boiling aromatichydrocarbons are subjected to a second high temperature catalytictreatment with a cracking or hydrocarbon splitting catalyst wherebycertain of the higher boiling aromatic hydrocarbons are decomposed toproduce additional toluene.- Other aromaticvhydro- .carbons notdecomposed or decomposable in the second stage of the process areseparated and employed as highknock rating motor fuel, high solvencynaphtha suitable for lacquer andpaint solvents, etc.

The process will b'readily understood by relferring to the drawingFwhich accompanies this spectdcation and is a part thereof. 'I'he draw-I ing shows diagrammatically ka. layout for a plant to produce tolueneand high knock rating mo r fuel from petroleum naphtha in accordance tmy invention.

plate I4.

ing of theV naphtha. The ycatalyst which is a porous, granular mass, issupported on perforated Catalysts of the `hydrogenatingde hydrogenatingtype are preferred, including the difllcultly reducible oxides such asvanadium,A chromium and molybdenum oxides and oxides of other metals inthe left columns of groups V and VI. It is preferred to employ theseoxides supported on a suitable base, particularly granular alumina ormagnesia. Activated alumina, magnesiteor bauxite activated by acid,treating may be employed as a base. The amount ofhydrogenating-dehydrogenating metal oxide 4supported on the aluminaforexample, may be of the order of 5 to 25%.

Hydrogen may be employed in the reactor I3, the hydrogen beingintroduced, for example, by line I5, and passed through the'furnace withthey naphtha. 'I'he amount of hydrogen may suitably equal the volume ofhydrocarbon vapors undergoing treatment or it may exceed that volume byas much as 2 to 5 vfold. When employing hydrogen, it is desirable tomaintainr the pres-- sure 'in reactor I3 within the range of 50 poundsto 600 pounds, preferably about to 250 pounds per square inch.. The rateof contacting the oil vapors with the catalyst in I3 may suitably beabout 0.2 to 5.0 volumes of liquid hydrocarbon per gross volume ofcatalyst per hour. The rate will depend partly on temperature, partly onthe character of thefstock and the activityA of the catalyst. Atemperature in reaction chamber I3 of fthe order 4of 900 to 1050 F. issatisfactory.

vapors leaving reactor I3 pass by line I6 to fractionator I1 where theyare fractionated 4several streams as indicated by the drawoff lines intoI8, I 9 and 20 and vapor line 2|. In the operation, the reflux in towerI1 is trapped out at different levels and the highest boiling fractionis withdrawn at the base of the fractionator by drawoff line 22. Thefraction withdrawn at line I9 is further fractionated in sidefractionator 23 where lighter materials are taken overhead and returnedby line 24 to main fractionator I1. A side cut boiling above about 115C., containing principally xylenes and heavier aromatic hydrocarbons, iswithdrawn by line 25 and employed in the blending' of motor fuel or as ahigh solvency is withdrawn by line 20 and is fractionated infractionator21 from which a toluene cut is With-v drawn by side drawoff line 28. Ahigher boiling fraction, containing in part xylenes and toluene, iswithdrawn from fractionator 21 via bottom drawoft line 29. This bottomfraction serves as part of the reflux in fractionator 23. Lightermaterials -in 21 are driven off from the toluene and returned to themain fractionator I1 by line 30.

Vapors from tower .I1 are conducted by line 2| to condenser 3I andreceiver 32 where fixed gases are separated and the light naphtha, whichis a W boiling light condensateis withdrawn by line 33. This stock maybe combined with the heavier naphtha in line 25 to Vproduce a motor fuelwhich is withdrawn by line 34.

i Stock which contains aromatics boiling within the range of from about146 C. to about 210 C. is trapped out at I8 from tower I1 and isconducted by line 35 to line 26 where it is combined with the bottomsfrom tower 23 and charged by pump 36 to coll 31- in heater 38 from whichthe hot oil vapors are conducted by line 33 to catalyst chamber 40.Different conversion conditions and different catalysts vare employed inchamber 40 from those employed in reactor I3. In chamber 40 theprincipal reaction is one of carbon to carbon bond rupture ratherthan-dehydrogenation and ring formation, typical of the catalyst andconditions the range of 950 to 1200 F. and thepredominant reactionappears to be a splitting or dealkylationtion by alkylation of thelighter alkyl aromatics in reactor 40 and hence the xylenes, toluene andbenzene are preferably removed from the feed passing to reactor 40'. Astock having an initial' boiling point of about 146 to 150 C. issuitable and this stock may be obtained by proper regu-,-

v lation of fractionatlng conditions in tower I1 and side fractionator23. .'I'hus, referring to tower 23 the xylene may constitute a largeproportion of the naphtha in line 25, which isemployed` for y in I3. In40 the temperature is preferably within 50 motor fuel or high solvencynaphtha. A heavier fraction withdrawn from tower I1 by line 35 and/orfrom fractionator `23 by line 26 may contain a large amount of alkylsubstituted toluene in which alkyl groups of 2 or more carbon atoms arepresent. Ethyl toluene having a boiling point of about 158. C. ischaracteristic of this material. Tower 40 yis filled with porous,granular catalyst of the conversion or splitting type such as activesilica, the alumina-silica complexes, acid treated clays, acid treatedbentonite, etc. Super Filtrol is an example of the latter type ofcatalyst. Silica gel impregnated with small amounts of magnesia,alumina, or with small amounts of alumina and zirconia may also be usedsupported on porous plate 4 I. Thevvapors pass downward through thecatalyst bed in reactor 40 and escape by line 42 leading to fractionator43.

Two side streams may be withdrawn from fractionator 43; the lower streamby line 44 has an initial boiling point of about 150 C. or higher and issuitable for blending with light naphtha from 32 making a motor ,fuel ofhigh knock rating which 'leaves the system by line 34 previouslydescribed. A part of this stream may be recycled to furnace 38 by line45 is desired. A toluene fraction is taken from tower 43 by line 41leading to side fractionator 48 where lighter fractions are eliminatedas overhead and relatively pure toluene -is withdrawn by side drawoii"line 49. A higher boiling fraction may be withdrawn from fractionator 48by line 50 leading to line 44. Alternatively, this heavy fraction may bereturned to the tower 43 for reuxing therein. The toluene removed byline 49 may be combined With the toluene in line 28 and discharged fromthe system by line 5I.

Vapors from fractionatcr 43 are led by line 52 to condenser 53 andreceiver 54 where the gases are separated and a light naphtha having aboiling range of about 30 to 110 C. may be led by line 55 into admixturewith the stocks from lines 25 and 33 to motor fuel line 34.

Residual fractions containing relatively high side fractions in tower I1may be conducted in regular manner previously described withoutsubstantial change. By this system of operation substituted toluenecompounds boiling above 150 C. are conducted by line 35 and pump 36 backto heater 38 where they are reprocessed until com' pletely convertedinto toluene.

As pointed out hereinabove, the conditions employed in reaction tower 40are generally more,

stringent than those employed in reaction chamber'l3. Contact ratesrepresented by space velocities of about 0.2 to 2 volumes `of oilcharged per hour perapparent volume of catalyst are characteristic. 950to 1050u F. and the pressure about atmospheric to 50 pounds per squareinch. The -prin cipal reaction occurring in reactor 40 is dealkylationof alkyl side chains on the aromatic nucleus. 'I'he amount of tolueneproduced in the .-operation of reactor 40 is, therefore, primarilydependent on the amount of polyalkylated benzene available in theprocess. In general. with average feed stocks,

such vagMid-lContinent' and East Texas naphtha The preferred temperatureis about" asesora side fractionator 48 as a'result of the-dealkylal tionof heavier substituted' aromatic hydrocarbons in reactor 40, thus makingthe total yield of toluene about 30%, based on the heavy naphtha chargedto heater I I.

It is believed that the reaction occurring in reactor I3 is largely oneofdehydrogenation and aromatization. High aromatic compounds may beconverted into aromatics by the former reaction and straight chainparaln compounds are also converted to aromatics by cyclization.`Hydrogen exerts a beneficial eiect upon the catalyst, increasing thecatalyst life and maintaining activity. lHydrogen for the process may beobtained' partially or ,entirely from the spent gases discharged fromseparator'1 32 where it'occurs in admixture with xedhydrocarbon gases.

When the catalysts in reactors I3 and 40 become spent they may berestored to substantially their original activity by oxidizing oil thecarbonaceous material with air vor mixtures of air with flue gas orother inert gas after purging the reactors of hydrocarbon vapors. Purgelines and catalyst regeneration lines are not shown on the drawing.

Although I have described my invention with respect to afspecicapparatus for carrying out the process, I do` not intend that it belimited except as described in the following claims.

I claim: i

1. The process of making toluene from vpetroleum riaphtha whichcomprises initially subjecting .said naphtha to catalytic conversioninthe presence of hydrogen and a hydrogenating-dehydrogenating catalystunder aromatizing conditions of ltemperature and pressure whereby said2. The processv of claim `1 wherein a xylene fraction is combined with afraction lighter than toluene to produce a motor' fuel of high knockrating.

3. The process of producing toluene from petroleum naphtha whichcomprises subjecting said naphtha to the action of a solidhydrogenatingf dehydrogenating catalyst ofthe metal oxide type 4in thepresence of hydrogen at a' temperature within the range of 900fto 1100F; and a space velocity of about 0.2 to 5`volumes per hour per volu-meof catalyst whereby aromatic hydrocarbons are produced, fractionatingsaid aromatic hydrocarbons and separatingl therefrom a toluene fraction,a xylene fraction and Ia fraction boiling between about 145 C. and 210C., subjecting said last-mentioned fraction to the action of a porous,

solid cracking catalyst at a pressure of about 0 to 50 pounds per squareinch gage, a temperaturewithin the range of 950 to 1150 F. and spacevelocity of about .2 to 2 volumes per hour per volurrie of catalyst,thereby converting a substantial amount of heavier aromatic hydrocarbonsinto toluene, and recovering said toluene 'from' the conversion productsby fractionation.'

4. The process of claim 3 wherein the hot converslonproducts obtainedfrom said cracking catalyst are conducted without condensation directlyto the fractionation step following said hydrogenation-dehydrogenationcatalyst treatment and fractionated therein to recover toluene.

5. 'I'he process of claim 3 wherein the said hy-"drogenation-dehydrogenation catalystis an oxide i I of a metal of theleft columns of groups V and VI of the periodic system. v

6. The process of cla-im 3 wherein the hydrocarbon cracking catalyst isa compound compris-v I ing essentially activated silica.

7. .'Ikhe process of producing toluene from paraiin hydrocarbonswhich`compri`ses subjecting a paralnlc petroleum naphtha to cyclizationin the presence of hydrogen and a dehydrogenating catalyst at acyclization temperature of about 900 to 1050 F., thereby converting asubstantial portion of the parailln hydrocarbon into toluene and otheraromatic hydrocarbons, separating from the aronaphtha is Asubstantiallyconverted into a mixture r' of aromatic hydrocarbons containingto1uene,` xylene and heavier aromatics, frationating said hydrocarbonsand removing therefrom a toluene fraction and a fraction heavierth'anxylene boilmatic hydrocarbon products a toluene fraction, a xylene`fraction' and a heavy fraction substantially all boiling above theboiling point of xylene,

subjecting said heavy fraction to the action of a porous, solid,cracking catalyst at a pressure of aboutO to 5 0 pounds per square inchgage and a temperature of about 950 to 1150 F., thereby converting heavyaromatic'hydrocarbons into lower square inch gage,` whereby additionaltoluene is v produced and separating said additional from the conversionproducts.

toluene boiling aromatic hydrocarbons including toluene,

and recovering the desired toluene from the products of said conversion.

ALEX G.. oBLAD.

